Longitudinal linewidth measurements of 10 GHz, picosecond mode-locked erbium-doped fiber lasers using a heterodyne detection method

摘要

Harmonically mode-locked erbium-doped fiber lasers, which operate in the 10～40 gigahertz region, have attracted widespread attention in the field of optical communication as light sources for ultra high-speed optical communication, because of their high-quality output pulses. However, the amount of longitudinal linewidth in these lasers has not yet been made clear. In this study, we measure the linewidth of a regeneratively and harmonically mode-locked erbium-doped fiber ring laser (ML Fiber Laser) for the first time by using a heterodyne method, and we show that the linewidth is less than 250 Hz.